Pharmacodynamics, principles of drug action

Question 1

What is receptor (R) theory?

Answer 1

2 step process:
1. Drug binding (affinity)
2. signal activation (efficacy) DR complex must signal to an effector to have an effect

Drug (D) + Receptor (R) <–[Affinity]–> DR complex –[Efficacy]–> Effector —> Response

Question 2

What is the law of mass action?

calc Ke and KD

Answer 2

the rate of chemical reaction is proportional to the product of the reactants.

Ke = KF/KR
KD, (dissociation constant) = KR/KF

Question 3

What is a drug.

Answer 3

A chemical applied to a physiological system that affects its function by increasing/decreasing physiological response.

Question 4

What are different types of antagonism?

Answer 4

**Pharmacological level: **
- 2 drugs competing for the same receptor: surmountable or insurmountable (allosteric or active site)
Tissue/organism level
- 2 drugs with opposing effects mediated by different mechanisms
Chemical level
- 2 unbound drugs combining in solution/binding to drug target in solution

Question 5

True or False

KD is a measure of affinity

Answer 5

True

Question 6

Factors affecting affinity

Answer 6

• concentration
• stability of complex formation
• molecular size
• shape
• electrical charge

Question 7

True or Fasle

EC50 is a measure of potency.

Answer 7

True

Potency is related to the dose required to produce a give degree of response.
EC50 is the concentration of drug required to produce therapeutic effects in 50% of the population.

Question 8

True of False

Emax is a measure of efficacy.

Answer 8

True

They are proportional

Question 9

What is efficacy?

Answer 9

• The ability of bound ligand to activate the receptor.
• Agonists elicit a direct response
• Antagonists has no efficacy at the receptor thus produce no direct response (no signalling mechanism)

Full agonists have an efficacy of 1
Partial agonists 0<efficacy<1
Antagonists efficacy = 0
Inverse agonists efficacy < 0

Question 10

(Intrinsic) pharmacological efficacy vs clinical efficacy of antagonists.

Answer 10

• Phamacological efficacy = 0 (no diresct response)
• Clincal efficacy is not 0 (because it is defined by the drug’s ability to achieve therapeutic outcomes)

Question 11

What is a graded drug response.

Answer 11

Response varies in magnitude in dose-dependent manner.

Normal dose-response curve

Question 12

What is quantal drug response.

Answer 12

Quantification of the # of subjects responding to the drug that varies in a dose-dependent manner.

Different drug concentration shows different # of indivs responding

Question 13

In the receptor theory, what does receptor refer to?

Answer 13

• CSM receptors
• ion channels
• enzymes
• transporters
• nucleic acids

Question 14

How do receptors affect selectivity of drug action?

Answer 14

Receptors are very specific, affecting:
1. Drug size
2. DR interactions (H2ID)
3. Drug shapes

Question 15

Its effects and how does it work

Mannitol

Answer 15

Mannitol is an osmotic diuretic.
- it is a large polar molecule
- creates osmotic gradient in tubular lumen, favoring water movement into tubular lumen for excretion

Question 16

Its effects and how does it work

Antacids: aluminium/magnesium hydroxide

Answer 16

neutralises stomach acids because they are alkaline

Question 17

Its effects and how does it work

Activated charcoal

Answer 17

• adsorption and detox binding to toxins
• non-specific binding to non-polar compounds with high molecular weight

Question 18

Its effects and how does it work

Chelating agents

Answer 18

-used for detox
- have multiple electron-donating groups to form dative bonds with metal ions (mercury), and forms a chemically stable shelate-complex

Question 19

Define PD

Answer 19

Pharmacodynamics refers to the relationship between drug concentration at the site of action and the resulting effect, including the time course and intensity of therapeutic and adverse effects.